基于Hopkinson杆的高g值加速度计的标定

介绍了基于Hopkinson杆技术的激光光栅干涉法冲击加速度计的绝对校准方法。采用激光干涉仪对激励信号进行测量,实现对高g值加速度计的标定。给出了高g值加速度传感器的灵敏度标定公式,并通过比较说明了两种公式的优缺点。实验结果表明,本文中的标定方法可满足标定的精度要求。     

CPU片上热敏元件及布局研究

CPU芯片内部温度的准确测量是保证微处理器发挥最佳性能和提高芯片可靠性的重要前提.在对晶体管参数热效应进行理论分析的基础上,提出一种基于晶体管集电极电流热效应的片上热敏元件方案,推导和仿真证实所提方案元件具有较高的转换灵敏度.在对CPU芯片热点温度场进行理论分析的基础上,建议一种根据温度场分布特点的拐点圆上敏感元件对称布局方案,推导证实所提方案可改善测量精度.     

FBG椭圆边孔封装的静水压力增敏技术研究

针对光纤光栅（FBG）的静水压力增敏及压力温度交叉敏感问题,提出光纤光栅的椭圆型边孔封装结构。采用有限元方法分析了封装结构中光纤光栅的力学效应,在此基础上得到优化的椭圆封装结构,并通过实验检验了理论分析结果。研究结果表明：优化的椭圆边孔封装结构中光纤光栅的静水压力灵敏度比裸光纤光栅高了4 198倍,而温度灵敏度仅增加了3.4倍,与裸光纤光栅相比,压力温度交叉敏感降低了1 760倍。该研究结果对光纤光栅压力传感器的实用化研究有参考价值。     

基于迈克耳孙干涉仪的凝视型激光告警系统设计

设计了一种基于迈克耳孙干涉仪的凝视型激光告警系统,理论分析了系统定向精度和滤光片透射率的变化规律。结果表明,入射激光经过告警系统后,形成环形干涉条纹,根据条纹中心的坐标和条纹间隔可解算入射激光的方向和波长;在探测器像元尺寸固定的情况下,系统的定向精度由光束变换透镜和球面反射镜焦距的比值决定,定向精度随该比值的减小而提高;告警系统滤光片的透射率取决于变换透镜的焦距,当变换透镜焦距为鱼眼镜头焦距10倍时,滤光片对系统入射角为0°~90°范围内激光的透射率为90.0%~87.5%,这保证了系统对各角度的入射激光都有较高的探测灵敏度。     

On the need for the use of error‐controlled finite element analyses in structural shape optimization processes

This work analyzes the influence of the discretization error associated with the finite element (FE) analyses of each design configuration proposed by the structural shape optimization algorithms over the behavior of the algorithm. The paper clearly shows that if FE analyses are not accurate enough, the final solution provided by the optimization algorithm will neither be optimal nor satisfy the constraints. The need for the use of adaptive FE analysis techniques in shape optimum design will be shown. The paper proposes the combination of two strategies to reduce the computational cost related to the use of mesh adaptivity in evolutionary optimization algorithms: (a) the use of an algorithm for the mesh generation by projection of the discretization error, which reduces the computational cost associated with the adaptive FE analysis of each geometrical configuration and (b) the successive increase of the required accuracy of the FE analyses in order to obtain a considerable reduction of the computational cost in the early stages of the optimization process. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient generation of pareto‐optimal topologies for compliance optimization

In multi‐objective optimization, a design is defined to beit pareto‐optimal if no other design exists that is better with respect to one objective, and as good with respect to other objectives. In this paper, we first show that if a topology is pareto‐optimal, then it must satisfy certain properties associated with the topological sensitivity field, i.e. no further comparison is necessary. This, in turn, leads to a deterministic, i.e. non‐stochastic, method for efficiently generating pareto‐optimal topologies using the classic fixed‐point iteration scheme. The proposed method is illustrated, and compared against SIMP‐based methods, through numerical examples. In this paper, the proposed method of generating pareto‐optimal topologies is limited to bi‐objective optimization, namely compliance–volume and compliance–compliance. The future work will focus on extending the method to non‐compliance and higher dimensional pareto optimization. Copyright © 2011 John Wiley & Sons, Ltd.     

基于GIS的风景名胜区生态敏感性分析——以重庆市南川金佛山风景名胜区为例

文章选择有区域代表性的生态因子,借助于GIS矢量叠加功能,采用加权叠加法,以金佛山风景名胜区为例,对其生态敏感性进行了深入分析,加强了风景名胜区规划的科学性和高效性。     

Elastic local post-buckling of elliptical tubes

The elastic local post-buckling behaviour of elliptical tubes under compression is analysed in this paper. A brief outline of the local, distortional and global buckling behaviour of EHS tubes is firstly provided, where it is shown that local buckling modes govern the stability of short to intermediate length tubes while distortional modes control the stability of intermediate length to moderately long tubes and global buckling dominates the behaviour of longer tubes. Following this, an in-depth numerical study employing shell finite element modelling, of the elastic local post-buckling behaviour of compressed elliptical hollow section (EHS) tubes is presented. It is concluded that EHS tubes with a low to moderate aspect ratio can support loads up to their limit loads but are imperfection sensitive (shell-type behaviour), while EHS tubes with a moderate to high aspect ratio can carry loads higher than their limit loads (plate-type behaviour) and are imperfection insensitive. The slope of the ascending post-buckling path increases with the EHS aspect ratio and can reach values up to 40% of the slope of the linear primary path. The bound imperfection amplitude concept, separating the imperfection amplitude ranges where the EHS tube is sensitive and insensitive, is proposed. It is also found that, for increasing EHS aspect ratio, the compressive stresses grow and accumulate near the zones of minimum radius of curvature while the zones of maximum radius of curvature possess an approximately uniform and relatively low compressive stress level. Therefore, it is expected that an approach based on the effective width concept widely used for the evaluation of the strength of flat plates may be adapted to the design of EHS tubes with moderate to high aspect ratios.     

煤岩冲击倾向性研究

 基于大量试验数据,系统分析煤岩冲击倾向性各种指标的相关数据,并针对现有行业标准中关于煤岩冲击倾向性评价存在的问题,提出将煤的单轴抗压强度作为评价煤层冲击倾向性的新指标,并给出判据;对原煤矿顶板岩层冲击倾向性指标的适用性进行分析,并指出不足,提出并推导出新的基于简支梁模型的顶板岩层冲击倾向性计算公式及其界定指标;分析脆性系数、含水率等与冲击倾向性之间的相关性。研究结果表明,煤的单轴抗压强度可以作为煤层冲击倾向性评价指标;依据简支梁模型确定的弯曲能量指数的计算公式,其计算结果与现场实际情况相吻合。     

抽水地面沉降中含水层长期变形特性研究

 长江三角洲地面沉降监测数据表明,抽水地面沉降中含水层的变形在总沉降量中占较大比例,且随时间长期发展。分析认为含水层砂土的蠕变是造成其变形长期发展的主要原因,而目前计算砂土蠕变特性的模型中普遍存在参数较多且确定困难的问题。根据含水层砂土的蠕变特性,对采用Singh黏性土蠕变模型计算含水层长期变形的方法进行研究。该模型假定土的蠕变速率与时间在双对数坐标系中呈线性关系,模型中仅有1个参数,即双对数坐标系中蠕变速率与时间曲线的斜率m。砂性土蠕变试验数据统计结果表明,砂性土的m值为0.9～1.1。通过对m的灵敏性分析可知,m在0.9～1.1区间内取值对计算结果影响不大,因此,在缺乏试验数据时可假定m = 1。利用常州和上海的地面沉降实测数据验证Singh模型计算含水层变形的有效性及模型参数简化确定方法的准确性。